I don't believe any laws truly prevent crime. If a person is determined to commit a crime, they will do it regardless of the possible consequences. However, laws do deter a lot of crime for people who are concerned about the consequences. I'm sure if we had a completely lawless society tomorrow, things would get out of hand within minutes.
At least hate crimes laws allow authorities to track hate crime incidents and the penalties incorporate hate-based crimes as a motive. Courts when determining punishment have always taken into account the motive. This is why a person who killed a spouse in a fit of rage would generally receive less time than someone who pre-planned a murder over an inheritance deal. Someone who goes around targeting people because of a group they belong to can be said to be terrorizing an entire community. While the person is no more dead or special than anyone else killed, the motive behind the killing and the results of it are more damaging to the society at large than some other types of murders. That is why I'm for hate crimes laws.
As to true prevention, most authorities will say that the more difficult you make yourself from becoming a victim, the more likely the criminal will find an easier target. This goes with just about any crime. A criminal could still defeat a steering wheel club on your car or get through ten locks on your house if they are truly determined but chances are they will target the next car or the next house with less security. If a serial killer is out there looking to harm TG people they are likely to go after the easiest victims. While we don't want to hear about any hate crimes ever happening, we can at least take steps to minimize it happening to us or our friends. If the sicko is watching you and you appear strong, difficult, and potentially a challenging fight and there is someone right across the street who is drunk, unalert, and appears helpless and stupid, they will likely go after that person. Nothing is 100% certain though. Be careful out there.